Photonic crystals were originally proposed by Eli Yablonovich and are based on the discontinuity in the index of refraction in a spatially-modulated structure. In one dimension, a photonic crystal is similar to a multilayer, dielectric mirror in which the index of refraction is alternated from layer-to-layer. Practical photonic crystals, such as the “log pile” structure, have typically been realized in solid materials by alternating, on a periodic basis, from one material to another. The crystals have been applied in numerous contexts, including optical communications, to achieve effective control over propagating electromagnetic waves. One drawback of photonic crystals constructed of two or more materials is that the properties of the crystal are fixed and not readily reconfigurable. Therefore, the electromagnetic properties of the crystal cannot be quickly varied with time.
Plasma has been proposed previously as a dielectric medium suitable for photonic crystals. See, Sakai, O., Sakaguchi, T., Ito, Y. & Tachibana, K., “Interaction and control of millimetre-waves with microplasma arrays,” Plasma Phys. Control. Fusion 47, B617-B627 (2005); Sakai, O. & Tachibana, K., “Plasmas as metamaterials: a review,” Plasma Sources Sci. Technol. 21, 013001 (2012); Sakai, O., Sakaguchi, T. & Tachibana, K., “Photonic bands in two-dimensional microplasma arrays,” I. Theoretical derivation of band structures of electromagnetic waves. J. Appl. Phys. 101, 073304 (2007). Sakai et al. demonstrated as photonic crystals two dimensional arrays of plasmas having electron densities (ne) in the range of 1011 to 1013 cm−3. Because of the size of the plasmas (nominally 2 mm in diameter) and the overlap between adjacent plasmas, the crystals reported were capable of only small attenuations at the wavelength(s) of interest. A one dimensional plasma photonic crystal was also proposed in Guo, B. “Photonic band gap structures of obliquely incident electromagnetic wave propagation in a one-dimension absorptive plasma photonic crystal”. Phys. Plasmas 16, 043508 (2009
The work of Tachibana and colleagues employed two dimensional (2D) microplasma arrays that produced spatially-disperse plasmas (i.e., not uniform in diameter). Attenuation of 60 GHz microwave signals was observed in these experiments but the magnitude of the suppression was small. Sakai et al. generated columnar plasmas ˜2 mm in diameter in a periodic, two-dimensional structure that had an overall area of 44 mm×44 mm, but converting this structure into three dimensions is problematic because of the electrode configuration and structure geometry. Guo proposed a one dimensional design for a plasma-based photonic crystal that similarly is not readily extendable to two or three dimensions. The weak attenuation of incident electromagnetic energy and the restriction of previous plasma photonic crystal designs to one or two dimensions suggest that the prior art does not offer structures capable of competing with photonic crystals fabricated from solids, or for capturing the inherent advantages that plasma-based photonic crystals have with respect to tunability and reconfigurability.